Oroville Spillway Update: 2/15

Tuesday afternoon the mandatory Evacuation Order was reduced to a warning. “An Evacuation Warning means the immediate threat has ended but the potential for an emergency remains and therefore residents must remain prepared for the possibility of an Evacuation Order,” said Butte County Sheriff Kory L. Honea.

The decision to reduce the Immediate Evacuation Order to an Evacuation Warning is based on a number of factors, including:

• Lower lake levels: With the rate of release through the primary spillway remaining at 100,000 cfs, over the last two days the lake level has dropped 12 feet below the top of the auxiliary spillway and no longer has water flowing over the top. This mitigation work will reduce the risk of erosion should the emergency spillway have to be used again, although flow through the primary spillway will continue to attempt to lower the reservoir to 851 feet (approximately 50 feet below capacity).

• Further inspections: With the water level reduced, geologists and dam safety engineering specialists from the Department of Water Resources (DWR), the Federal Energy Regulatory Commission (FERC) and the United States Army Corps of Engineers were able to inspect the damage. That inspection revealed that the integrity of the emergency spillway was not compromised by the erosion.

• Ongoing work to shore-up emergency spillway: To prevent further erosion the DWR is lining the front of the spillway with boulders and concrete. That work is expected to be completed tomorrow, ahead of the forecasted stormy weather.

• Updated weather forecasts: The decision has taken into account updated weather forecasts. The storm expected later this week is forecasted to be colder, with less rain and therefore a lower level of water flow into the reservoir than last week.

An evacuation center will remain open at the Silver Dollar Fairgrounds. All other evacuation centers supported by Butte County will be closed. Residents from other centers who are still seeking shelter due to the Evacuation Warning can go to the Silver Dollar Fairgrounds.

For information on lake conditions; including lake levels, inflows, and outflows you can visit the following website: http://cdec.water.ca.gov/cdecapp/resapp/resDetailOrig.action?resid=ORO